An urgent need exists for a rapid, real-time determination of radiation damage to a person who has been exposed to gamma and/or neutron radiation.
It is well known that radiation breaks bonds between atoms in molecules. When the bonds are broken homolytically, free radicals result. When the bonds are broken heterolytically (diamagnetic), ionic fragments result. The free radicals, unlike ionic fragments, can be seen by EPR. Therefore, the technique for determining radiaion damage to a person by use of EPR is based on the amount and type of free radicals that are generated due to the radiation exposure. It has been suggested by experts in this field that a finger or tooth are potentially good constituents of the human body to utilize for performing EPR measurements to determine the extent of radiation damage. The free radicals, for example, in the bone, resonate when exposed to radio frequency (RF) photons in the X-Band (6.2-10.9 gigahertz (GHz). A currently used method of exposing the sample that is to be analyzed to microwave energy is to place the sample in a passive, high Q-factor microwave cavity. The inside cross-sectional dimensions of an X-band cavity or waveguide are typically 0.4 by 0.9 inches for the 8.2 to 12.4 GHz frequency range. An X-Band rectangular cavity would have a length equal to an integral number of one-half waveguide wavelengths. One can easily see from these dimensions that a finger would occupy a considerable part of the cavity volume. This being the case, there exists a serious technical barrier (excessive loss that reduces the cavity factor) to overcome before a finger can be utilized as the sample to be analyzed for radiation damage by EPR. A finger, being large and dielectrically lossy, will load down a high Q-factor passive microwave X-Band cavity to a significant degree so that the EPR sensitivity will be drastically reduced, inhibiting any satisfactory measurements. In addition, a small frequency shift will occur which further reduces sensitivity.